1. Field of the Invention
The present invention relates to a keyboard device of an electronic musical instrument and more particularly to a keyboard device of an electronic keyboard instrument which enables a player to feel substantially the same sense of touch as that in a common piano by eliminating a sense of friction which may be exerted upon his finger when pushing down a key.
2. Description of the Prior Art
A keyboard device of a prior art electronic keyboard instrument, as shown in FIG. 1 of the accompanying drawings, comprises an actuator (2) projecting downwardly from a lower surface of a keyboard(1) and movable up and down therewith, and a switch(3) fixedly secured to a main plate(4) at a position below the actuator(2) to be actuated by the descending actuator. The keyboard(1) also has at its forward end a downwardly protruding stopper(5) which engages with a groove formed in the main plate(4) to limit the upward movement of the keyboard (1). Further, a keyboard guide(6) is disposed on the underside of the keyboard(1), and a keyboard guider(7) is fixedly secured to the main plate(4) to guide the keyboard guide(6) during the upward and downward movements of the keyboard(1). A rear end of the keyboard(1) having an insertion groove(9) is inserted into a hinge hole(4a) of the main plate(4) to form a pivoting point about which the keyboard pivots. In addition, a coil spring(8) is mounted between the lower surface of the keyboard(1) and the main plate(4) to bias upwardly the keyboard. With this construction, when the keyboard(1) is not actuated, it is maintained in a horizontal position by the coil spring(8) urging the keyboard upwardly and the stopper(5) limiting the upward movement of the keyboard.
In the prior keyboard device as described above, therefore, when a player presses down the keyboard(1) for playing the musical instrument, the keyboard is pivoted downwardly about the pivoting point of its rear end while compressing the coil spring(8). As a result, the downwardly protruding actuator(2) descending together with the keyboard contacts the switch(3) to switch on it, thereby generating a sound of the electronic musical instrument. In this state, upon withdrawal of his finger from the keyboard, the keyboard returns to its original position by the resilient restoring force of the compressed coil spring(8) and the switch(3) is switched off, whereby the generation of sound stops.
This prior keyboard device however has a drawback in that because the keyboard is simply supported resiliently only by the coil spring, the more the player presses down the keyboard, the more heavy his finger feels. This can be seen in the graph of FIG. 2 illustrating Force-Stroke characteristic curves (F-S diagram) of the common piano indicated by a dotted line and the prior electronic piano indicated by a solid line. The keyboard device of the prior electronic musical instrument makes the player need use force which abruptly increases in proportion to an increase in key stroke, as compared with the common piano, so that the more the player pushes down the keyboard, the more heavy his finger feels. Particularly, in the electronic keyboard instrument, since the player must continue to push down the keys for one cord by the fingers of his left hand until the cord is changed, he feels considerably heavier pushing force than that in the common piano.